The present invention relates generally to polymeric compositions. More particularly, the present invention relates to polymeric compositions useful in the manufacture of hoses for use in the automotive industry.
Hoses, particularly rubber hoses, are used in a variety of applications in the automotive industry as fuel feed hoses, torque converter hoses, power steering hoses and air conditioner hoses; as well as for industrial and household utility applications such as hydraulic hoses, refrigeration hoses, washing machine hoses, propane gas feed hoses, high pressure air hoses, garden hoses, etc.
It is generally known that rubber surfaces do not always exhibit desired resistance against chemical loads such as organic gases and solvents. Therefore, other approaches for improving the organic gas and solvent resistance of rubber materials included using rubber materials which have a different polarity than the organic gas or solvent, increasing the crosslinking of the rubber material, adding or increasing certain additives, and increasing the wall thickness of the rubber tube material. All of these approaches have a down side. For example, the use of a rubber material having a polarity different from the organic gas or solvent requires the use of more expensive rubber materials such as chloroprene rubber, acrylic rubber, epichlorohydrin rubber, and the like; increasing the degree of crosslinking of the rubber used detracts from the softness and flexibility of the rubber; the addition of additives affects the processability and certain physical properties of the rubber; and increasing the wall thickness of the rubber material also increases the weight of the structure. Generally, these undesirable effects overshadow any advantage gained in the improved gas and solvent resistance.
In order to improve the impermeability of multilayered rubber hoses, typical approaches include the use of a metal film as a barrier layer coated on one of the inner layers. Such disclosures appear, for example, in U.S. Pat. No. 318,458 to Fletcher where there is disclosed a multilane tubular structure made from India rubber and having a tin foil liner. Other prior art patents such as U.S. Pat. No. 4,559,793 to Hanes et al.; U.S. Pat. No. 4,759,455 to Campbell et al.; U.S. Pat. No. 5,182,147 to Davis; U.S. Pat. No. 5,271,977 to Yoshikawa et al; U.S. Pat. No. 5,360,037 to Lindstrom; U.S. Pat. No. 5,398,729 to Spurgat; and U.S. Pat. No. 5,476,121 to Yoshikawa et al. have attempted similar methods to reduce the permeability of fluids and/or gases through various tubes. Commonly assigned U.S. Pat. No. 6,074,717 to Little et al.; and U.S. Pat. Nos. 4,779,673 and 5,488,975 to Chiles et al. disclose metal coated synthetic rubber hoses used for circulation of fluids in radiant heating systems in houses and in businesses and disclose the use of an inner nylon tubular layer having a metal layer surrounding the nylon layer.
Polymeric material used to form the hose for accommodating fluids and gases under elevated pressures and/or high temperatures such as in automotive air conditioner cooler hoses and power steering hoses must meet other critical requirements. For example, the polymeric material must exhibit low permeability to FREON or other coolant gases to prevent such gases from escaping from the hose. Also such polymeric hose must be able to prevent outside moisture from entering the interior of the hose where it could contaminate the fluid or gas. In addition, the polymeric hose must be capable of withstanding high heat and pressure, be able to withstand engine and impact vibration, and be capable of forming gas-tight connections.
In the case of hoses for accommodating coolant fluid for automotive air conditioners, etc., polymeric materials such as polychloroprene (CR), acrylonitrile-butadiene rubber (NBR), chlorosulfonated polyethylene (CSM), chlorinated polyethylene (CPE), polyacrylate (PA), ethylene-acrylic rubber (AEM), alkyl acrylate copolymer (ACM), polyvinyl acetate, acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (HNBR), ethylene-propylene-diene terpolymer (EPDM), cis-polybutadiene, cis-polyisoprene, polyurethane, polyamides such as nylon are often used as the material for forming the hose. For example, nylon 6 and nylon 66 are very low in coolant gas permeability, but are relatively high in moisture permeability. On the other hand, nylon 11 and 12 are relatively low in moisture permeability and less susceptible to hydrolysis, but are moderately high in gas permeability. Blends of any of the various nylons with other nylons, olefins or other materials are also used in such applications. For example, blends such as nylon 6, nylon 4, nylon 66, nylon 11, nylon 12, have been made to take advantage of desirable characteristics of one or more of such nylons and, at the same time, reduce the effects of any undesirable characteristics. However, blending the various polymeric material for the purpose of obtaining the desired benefits of each individual component actually acts to reduce the desired benefit because of the dilution effect of the other component(s) employed. Therefore, while one can obtain a variety of benefits by blending various polymers, the actual observed benefits may be reduced.
Ethylene-vinyl acetate copolymer (VAE) compositions are known. For example, U.S. Pat. Nos. 4,338,227 6,492,454; 5,942,580; 5,837,791; 5,830,941; 5,807,948; 5,744,566; 5,698,651; 5,362,533; 5,135,988; 4,338,227 and 4,309,332 describe various ethylene-vinyl acetate copolymers and the uses thereof. Copolymers of ethylene and vinyl acetate exhibit elastomeric characteristics and are commonly used to improve adhesion properties of hot melt, solvent-based and pressure-sensitive adhesives. It is generally well known that the use of ethylene-vinyl acetate copolymers in the automotive industry and commercial applications are mostly limited to coatings, adhesives, gaskets, O-rings and the like. For example, “Ultrathene”, a series of ethylene-vinyl acetate copolymers manufactured by Quantum Chemical, is typically used for adhesives, conversion coatings and thermoplastic modifiers. Such EVA copolymers exhibit a wide range of melt indexes. Ethylene-vinyl acetate copolymers are also marketed by Bayer under the trade name “Levapren”. These EVA copolymers are described as oil and heat resistant materials which may be used in air hose applications. U.S. Pat. No. 6,605,327 to Ramey et al. teaches the use of two separate layers of an ethylene-vinyl copolymer in the manufacture of a multilayer hose.
Blends of vinyl esters with other polymers have been found to be somewhat effective in the manufacture of automotive hoses. For example, blends of ethylene-vinyl acetate with ethylene-vinyl acetate-carbon monoxide terpolymers are useful in applications were flame retardant, low smoke, oil resistant flexible systems are desirable as coatings such as coatings for wire and cable construction, are described in U.S. Pat. No. 6,133,367 to Arhart. However, there is no mention in the prior art of blends of a first vinyl ester with second copolymer selected from the group consisting of chlorosulfonated polyethylene (CSM), chlorinated polyethylene (CPE), polychloroprene (CR), acrylonitrile-butadiene rubber (NBR), polyacrylate (PA), ethylene-acrylic rubber (AEM), alkyl acrylate copolymer (ACM), polyvinyl acetate, acrylonitrile-butadiene rubber (NBR), hydrogenated acrylonitrile-butadiene rubber (HNBR), ethylene-propylene-diene terpolymer (EPDM), cis-polybutadiene, cis-polyisoprene.
Ethylene-vinyl acetate copolymers and blends thereof have been employed in the wire and cable industry as a sheath or cover material surrounding electrical wires. For example, polymeric blends of ethylene-vinyl acetate copolymers with ethylene-vinyl acetate-carbon monoxide terpolymers which are particularly useful in applications where flame retardant, low smoke, oil resistant, flexible systems are desirable as a wire coating. Patents disclosing the use of ethylene-vinyl acetate copolymers as wire and cable coatings include U.S. Pat. No. 4,349,605 to Biggs et al.; U.S. Pat. No. 4,381,326 to Biggs et al; U.S. Pat. No. 4,477,523 to Biggs et al.; U.S. Pat. No. 5,191,004 to Maringer et al.; U.S. Pat. No. 5,225,460 to Maringer et al.; and U.S. Pat. No. 5,226,489 to Maringer et al. None of the references describe a self supporting tubular structure, nor is there any teaching of a blend of a first vinyl ester and a second copolymer selected from the group consisting of polychloroprene (CR), acrylonitrile-butadiene rubber (NBR), chlorosulfonated polyethylene (CSM), chlorinated polyethylene (CPE), polyacrylate (PA), ethylene-acrylic rubber (AEM), alkyl acrylate copolymer (ACM), polyvinyl acetate, hydrogenated acrylonitrile-butadiene rubber (HNBR), ethylene-propylene-diene terpolymer (EPDM), cis-polybutadiene, cis-polyisoprene.
Choosing the right material or combination of materials to be used in the construction of automotive hoses is becoming more and more difficult because the hoses are now required to withstand higher pressures and temperatures than previous hoses performing the same tasks. Also mandated regulations require that the hoses exhibit greater impermeability rates and resist stress over longer periods of time while maintaining manufacturing costs at an acceptable level. Therefore, the manufacturers of automotive hoses find it necessary to come up with newer and better materials and combinations of materials to meet these rising needs. In order to achieve a material which meets regulations and still retains the many desirable characteristics necessary to satisfy the manufacturer, attempts have been made to blend various materials which individually exhibit the desirable characteristics. However, it is generally found that, while these blended composite materials may exhibit all of the desirable characteristics, these desirable characteristics have been drastically diluted to the point where the material is no longer acceptable.
Accordingly, in the manufacture of hoses for the automotive industry, it would be desirable to find a material blended from two or more individual polymers, each of which exhibits one or more desirable characteristics, wherein the individual characteristics in the resulting blend are not diluted by the other polymers.